VMS to GSM Converter
Processing entirely on your device — large files may take a moment.
VMS is the cropped ADPCM dialect used by answering machines and dictation recorders — dialects of Dallas Semiconductor's timekeeping chips. Convert GSM speech recordings to WAV or MP3.
iLoveConverter processes everything locally on your computer, which makes it private and fast: no upload wait, no server storage, no limits. Add as many files as you like — batch conversion is built in.
How VMS compares to GSM
| VMS | GSM | |
|---|---|---|
| Structure | Voice Mail System container | Raw GSM frames (33 bytes/20ms) |
| Compatibility | ffmpeg, archive tools | Asterisk, SoX, ffmpeg |
| Best for | Rescuing legacy audio | Telephony recordings |
How to convert VMS to GSM
- 1
Select your files
Drag & drop your VMS files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to GSM". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted GSM file individually, or grab everything at once as a ZIP archive.
About the VMS format
FSSD is a raw 8-bit audio dump format from early UNIX sound experiments — tiny headers, bare samples.
ffmpeg decodes it natively inside your browser — the audio track is re-encoded to your chosen format with nothing ever uploaded.
+ Strengths
- ✓Decoded natively by ffmpeg
- ✓Runs entirely in your browser
- ✓Free, private, no watermarks
! Limitations
- −Legacy niche format
- −Modern tools rarely open it
- −Keep the original for archival round-trips
About the GSM format
GSM 06.10 is the speech codec of the original GSM mobile network — 13 kbit/s RPE-LTP that made digital cellphone calls possible in 1991 and still lives inside VoIP systems, old answering machines and Asterisk PBX recordings.
It is lossy speech, not music: converting GSM to WAV or MP3 preserves intelligibility perfectly while finally letting desktop players open the file without special codecs.
+ Strengths
- ✓Tiny bitrate for speech intelligibility
- ✓Ubiquitous in telephony systems
- ✓Decodes natively via ffmpeg
! Limitations
- −Speech-only quality — music falls apart
- −13 kbit/s artifacts are audible
- −8000 Hz sample rate only
Why convert VMS to GSM?
Converting makes sense where the strengths of GSM meet what VMS cannot give you. Tiny bitrate for speech intelligibility Meanwhile Legacy niche format One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this VMS to GSM converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for VMS to GSM?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Will converting VMS to GSM reduce audio quality?
If GSM is lossless, the output contains everything the VMS file contains — no further loss is added. If GSM is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.
Can I convert a whole folder of VMS files?
You can select many files at once and they are processed in a single batch. Output files land in one ZIP download when there is more than one result.